CN108780344B

CN108780344B - In-plane active cooling device for mobile electronic devices

Info

Publication number: CN108780344B
Application number: CN201780018440.1A
Authority: CN
Inventors: P·王; U·瓦达坎玛卢维多; V·米特
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2016-03-30
Filing date: 2017-03-28
Publication date: 2021-03-12
Anticipated expiration: 2037-03-28
Also published as: EP3436892B1; BR112018069655A2; US10267545B2; CA3015939A1; EP3436892A1; US20170284708A1; CN108780344A; JP2019517128A; WO2017172752A1; KR20180130508A; TW201806204A

Abstract

An active heat transfer device for heat management in an apparatus such as a mobile device is proposed. The proposed heat transfer device may include a Thermoelectric (TE) layer, and first and second electrodes both on lateral surfaces of the TE layer. When a voltage difference exists between the first and second electrodes, heat from the heat source may be transferred laterally within the TE layer from the first electrode to the second electrode.

Description

In-plane active cooling device for mobile electronic devices

FIELD OF THE DISCLOSURE

Various aspects described herein relate to thermal management in electronic devices, and more particularly, to in-plane active cooling devices.

Background

Thermal management can be critical to systems such as mobile devices. This is because in most use cases the system performance is thermally limited by the maximum allowable junction temperature. Housing temperature can be another important design constraint because high surface temperatures can make the device uncomfortable to use or can cause local skin burns. For example, Original Equipment Manufacturers (OEMs) typically require 45 ℃ as the maximum allowable temperature for plastic surfaces and 40 ℃ as the maximum allowable temperature for metal surfaces. Thus, system performance is sometimes thermally limited by the enclosure temperature.

Accordingly, in systems such as mobile electronic devices, it would be desirable to address one or both of the comfortable surface touch temperature and maximum temperature limits of critical internal components, such as a Central Processing Unit (CPU), Graphics Processing Unit (GPU), Power Management Integrated Circuit (PMIC), and the like. Generally, cooling solutions for mobile devices are software-based thermal mitigation and thermal/mechanical-based passive heat dissipation.

Overview

This overview identifies features of some example aspects and is not an exclusive or exhaustive description of the disclosed subject matter. Whether features or aspects are included in or omitted from this overview is not intended to indicate relative importance of the features. Additional features and aspects are described and will become apparent to those of ordinary skill in the art upon reading the following detailed description and viewing the drawings that form a part hereof.

One or more aspects relate to a heat transfer device configured to actively transfer heat. The thermal transfer device may include a Thermoelectric (TE) layer, a first electrode, and a second electrode. The TE layer may have a first lateral surface, a second lateral surface, a first side surface, and a second side surface. The first and second lateral surfaces may be longer than the first and second side surfaces. The first electrode may be on the first lateral surface of the TE layer and may interface with the TE layer at a first junction. The second electrode may be on the first lateral surface or the second lateral surface of the TE layer and may interface with the TE layer at a second junction. The heat transfer device may be configured to: heat generated by a heat source is transferred laterally within the TE layer from the first electrode to the second electrode when a voltage difference exists between the first electrode and the second electrode.

One or more aspects relate to an apparatus that may include a chip, a battery configured to provide power to the chip, and a heat transfer device configured to actively transfer heat away from the chip. The thermal transfer device may include a Thermoelectric (TE) layer, a first electrode, and a second electrode. The TE layer may have a first lateral surface, a second lateral surface, a first side surface, and a second side surface. The first and second lateral surfaces may be longer than the first and second side surfaces. The first electrode may be on the first lateral surface of the TE layer and may interface with the TE layer at a first junction, which may overlap the chip. The second electrode may be on the first lateral surface or the second lateral surface of the TE layer and may interface with the TE layer at a second junction. The heat transfer device may be configured to: when the battery causes a voltage difference between the first electrode and the second electrode, heat generated by the chip is transferred laterally within the TE layer from the first electrode to the second electrode.

One or more aspects relate to a method of forming a heat transfer device for actively transferring heat. The method may comprise: forming a Thermoelectric (TE) layer, forming a first electrode, and forming a second electrode. The TE layer may be formed to have a first lateral surface, a second lateral surface, a first side surface, and a second side surface such that each of the first lateral surface and the second lateral surface is longer than each of the first side surface and the second side surface. The first electrode may be formed on the first lateral surface of the TE layer such that the first electrode interfaces with the TE layer at a first junction. The second electrode may be formed on the first lateral surface or the second lateral surface of the TE layer such that the second electrode interfaces with the TE layer at a second junction. The heat transfer device may be formed such that heat generated by a heat source is transferred laterally within the TE layer from the first electrode to the second electrode when a voltage difference exists between the first electrode and the second electrode.

One or more aspects relate to a heat transfer device configured to actively transfer heat. The heat transfer device may include a Thermoelectric (TE) layer, means for applying a first voltage, and means for applying a second voltage. The TE layer may have a first lateral surface, a second lateral surface, a first side surface, and a second side surface. The first and second lateral surfaces may be longer than the first and second side surfaces. The means for applying a first voltage (e.g., a first electrode) may be on the first lateral surface of the TE layer and may interface with the TE layer at a first junction. The means for applying a second voltage (e.g., a second electrode) may be on the first lateral surface or the second lateral surface of the TE layer and may interface with the TE layer at a second junction. The heat transfer device may be configured to: transferring heat laterally within the TE layer from the means for applying a first voltage to the means for applying a second voltage when there is a voltage difference between the means for applying a first voltage and the means for applying a second voltage.

Brief Description of Drawings

The accompanying drawings are presented to aid in the description of examples and are provided solely for illustration of the examples and not limitation thereof.

Fig. 1 and 2 illustrate a conventional thermoelectric cooler for explaining thermoelectricity and operation;

FIGS. 3A and 3B illustrate top and side views of a thermoelectric cooler according to a non-limiting aspect of the present disclosure;

FIGS. 4A and 4B illustrate top and side views of a thermoelectric cooler according to a non-limiting aspect of the present disclosure;

5A, 5B, and 5C illustrate a top view, a first side view, and a second side view of a thermoelectric cooler according to a non-limiting aspect of the present disclosure;

FIG. 6 illustrates an apparatus incorporating a heat transfer device according to a non-limiting aspect of the present disclosure;

fig. 7A and 7B illustrate exemplary details of a heat transfer device incorporated into an apparatus according to a non-limiting aspect of the present disclosure;

8, 9, 10, and 11 illustrate examples of an apparatus incorporating a heat transfer device according to non-limiting aspects of the present disclosure;

12A-12C illustrate stages of a method for forming a heat transfer device according to a non-limiting aspect of the present disclosure;

FIG. 13 illustrates a flow diagram of a method for forming a heat transfer device in accordance with non-limiting aspects of the present disclosure;

14A-14C illustrate stages of another method for forming a heat transfer device according to a non-limiting aspect of the present disclosure; and

fig. 15 illustrates a flow diagram of another method for forming a heat transfer device according to a non-limiting aspect of the present disclosure.

Detailed Description

Aspects are provided in the following description and related drawings directed to specific examples of one or more aspects of the present disclosure. Alternative examples may be devised without departing from the scope of the present discussion. Additionally, well-known elements will not be described in detail or will be omitted so as not to obscure the relevant details.

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any example described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other examples. Likewise, the term "embodiments" does not require that all embodiments of the disclosed subject matter include the discussed feature, advantage or mode of operation.

The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Further, many examples are described in terms of sequences of actions to be performed by, for example, elements of a computing device. It will be recognized that various actions described herein can be performed by specific circuits (e.g., Application Specific Integrated Circuits (ASICs)), by program instructions being executed by one or more processors, or by a combination of both. Additionally, the sequence of actions described herein can be considered to be embodied entirely within any form of computer readable storage medium having stored therein a corresponding set of computer instructions that upon execution would cause an associated processor to perform the functionality described herein. Thus, the various aspects may be embodied in several different forms, all of which have been contemplated to be within the scope of the claimed subject matter. Additionally, for each example described herein, the corresponding form of any such example may be described herein as, for example, "logic configured to" perform the described action.

As mentioned, conventional thermal management for mobile devices includes software-based thermal mitigation and thermal/mechanical-based passive heat dissipation. Alternatively or in addition thereto, it is proposed to provide thermal management with a heat transfer device that actively transfers heat. The proposed heat transfer device may be used alone or in combination with software-based thermal mitigation and/or passive thermal/mechanical-based passive heat dissipation.

Thermoelectric coolers (TECs) are examples of active heat transfer devices. TEC is a solid state pump that uses the phenomenon of electrical energy-thermal energy conversion to pump heat from one side to the other to achieve active cooling. The principle of TEC operation is illustrated in fig. 1. As illustrated, TEC 100 may include a Thermoelectric (TE) material 150 between first and

second electrodes

110, 120, respectively. The TE material 150 may be an N-type or P-type semiconductor and the first and

second electrodes

110, 120 may be metallic.

The thermoelectric physics are briefly explained. When two different materials (e.g., metal and semiconductor) are joined together and current flows through the junction of the two materials, heat is absorbed or released at the junction between the different materials, depending on the direction of current flow and the type of semiconductor. At the junction where the heat is absorbed, cooling occurs. Instead, at the junction where the heat is released, heating occurs. In fig. 1, there are two junctions highlighted by dashed ellipses — a first junction 112 between the first electrode 110 and the TE material 150, and a second junction 122 between the TE material 150 and the second electrode 120.

When power is applied to the first and

second electrodes

110, 120, heat is absorbed at one junction and released at the other junction. Thus, heat flows from one electrode to the other. If the voltage difference is such that the voltage applied to the first electrode 110 is higher than the voltage applied to the second electrode 120, current flows from the first electrode 110 to the second electrode 120 within the TE material 150 (assuming current flow is considered to be opposite to the flow of electrons). If the TE material 150 is a P-type semiconductor, heat is pumped from the positive voltage side to the negative voltage side in the direction of current flow. In other words, heat is absorbed at the first junction 112 and released at the second junction 122. If the TE material 150 is an N-type semiconductor, heat is pumped in the opposite direction to the current-from the negative voltage side (where heat is absorbed at the second junction 122) to the positive voltage side (where heat is released at the first junction 112).

The thermoelectric cooling and heating power Q is proportional to the absolute temperature T, the applied current I, and the seebeck coefficient S, and can be given by Q ═ STI. The cooling power Q occurring at the heat absorption junction_CCan be expressed as Q_C＝ST_CI. Similarly, the heating power Q occurring at the heat release junction_HCan be expressed as Q_H＝ST_HI. However, additional heat is also generated due to the current flowing through the TE material 150. Such Joule heating Q_JCan be quantized to Q_J＝I²R, where R is the resistance of the current path. Assuming that the first and

second electrodes

110, 120 are metal, most of the resistance will be due to the TE material 150. Assuming TE material 150 is a P-type semiconductor, these three thermal powers are illustrated in fig. 2: q_C、Q_HAnd Q_J。

Thermoelectric cooling efficiency can be characterized by the coefficient of performance (COP), which can be defined as the ratio of heat pumped to power input. At one angle, the heat pumped may be equivalent to the cooling power Q_C. COP generally depends on the temperature difference between the cold side and the hot side. This means that COP is inversely related to temperature difference, e.g., COP decreases as temperature difference increases.

As indicated above, it is proposed to provide thermal management using active heat transfer devices (such as TEC). However, conventional cross-plane TECs are not suitable for use in mobile devices because of the fact thatThe small form factor of mobile devices makes it difficult to accommodate millimeter-scale TEC and does not provide sufficient capability to remove the thermoelectric heat STI and the Joule heat I²And R is shown in the specification. Another limitation of conventional TECs is that when integrated into a mobile device, the TEC makes the junction cooler and the housing hotter, or makes the housing cooler and the junction hotter.

To address one or more shortcomings of conventional thermal management solutions, it is proposed to integrate an in-plane active cooling device that is capable of transferring heat laterally from a hot area to a cold area of a mobile device. One or more aspects of the proposal may enable effective thermal management by reducing both junction temperature and case hot spot temperature.

A non-limiting example of a heat transfer device 300, such as a thermoelectric cooler (TEC), is illustrated in fig. 3A and 3B. The heat transfer device 300 is an active heat transfer device. Fig. 3A illustrates a top view and fig. 3B illustrates a side view. The heat transfer device 300 may have an in-plane configuration that allows heat to be pumped laterally. As seen, the heat transfer device 300 may include a Thermoelectric (TE) layer 350, a first electrode 310, and a second electrode 320. The first electrode 310 may be an example of a means for applying a first voltage, and the second electrode 320 may be an example of a means for applying a second voltage. The TE layer 350 may be an N-type or P-type semiconductor and may have first and second lateral surfaces 352, 354 and first and second side surfaces 356, 358 (see fig. 3B). From one perspective, the first and second lateral surfaces 352, 354 are referred to as lateral surfaces because they are longer than the first and second side surfaces 356, 358. For convenience, the first and second lateral surfaces 352, 354 and the first and second side surfaces 356, 358 may also be referred to as upper, lower, left and

right surfaces

352, 354, 356, 358. It should be noted that the adjectives up, down, left and right are merely for convenience and should not be used to indicate absolute orientation.

The first electrode 310 may be on one lateral surface of the TE layer 350-either the upper surface 352 or the lower surface 354. Where the first electrode 310 and the TE layer 350 interface with each other may be referred to as a first junction 312. In this example, "docked" may be synonymous with "contacted". For ease of discussion, it will be assumed that the first electrode 310 is on the first lateral surface 352 of the TE layer 350. From one perspective, the first junction 312 may be considered to be part of the first lateral surface 352.

In one aspect, the first electrode 310 is highly electrically and thermally conductive. For example, the first electrode 310 may be a metal. The first electrode 310 may be located at or substantially at one end of the TE layer 350. In fig. 3B, the first electrode 310 is illustrated as being flush or substantially flush with the left surface 356 of the TE layer 350 and extending toward the right surface 358. Since the first electrode 310 interfaces with the TE layer 350 at the first junction 312, it can be considered that the first junction 312 may begin or substantially begin at the first side surface 356 and extend toward the second side surface 358.

The second electrode 320 may also be on the upper surface 352 of the TE layer 350 such that the second electrode 320 and the TE layer 350 interface with each other at the second junction 322. That is, the second junction 322 may also be a portion of the first lateral surface 352. Similar to the first electrode 310, the second electrode 320 may be highly electrically and thermally conductive, such as a metal. The second electrode 320 may be formed of the same or different material as that used to form the first electrode 310. The second electrode 320 may be located at or substantially at the end of the TE layer 350 opposite the end where the first electrode 310 is located. In fig. 3B, the second electrode 320 is illustrated as being flush or substantially flush with the right surface 358 of the TE layer 350 and extending toward the left surface 356. Since the second electrode 320 interfaces with the TE layer 350 at the second junction 322, it can be considered that the second junction 322 can begin, or substantially begin, at the second side surface 358 and extend toward the first side surface 356.

In fig. 3A and 3B, it may be assumed that heat flows laterally within the TE layer 350 (left to right in these figures) from the first electrode 310 to the second electrode 320 when there is a voltage difference between the first electrode 310 and the second electrode 320. That is, when power is applied between the first and

second electrodes

310, 320, heat may be absorbed at the first junction 312 and released at the second junction 322. If the TE layer 350 is a P-type semiconductor, the voltage potential applied to the first electrode 310 should be high. If the TE layer 350 is an N-type semiconductor, the potential applied to the second electrode 320 should be high.

A heat source 305 is shown in fig. 3A and 3B. The heat source 305 may be a chip (such as a CPU, GPU, PMIC), or any device to be cooled. The heat source 305 itself need not be part of the heat transfer device 300. Rather, in one aspect, the heat source 305 is shown to indicate that the first electrode 310 is located nearby. In this manner, heat generated by the heat source 305 may be absorbed at the first junction 312 by the first electrode 310, transferred laterally through the TE layer 350, and released at the second junction 322 by the second electrode 320. To enhance efficiency, heat conduction from the heat source 305 to the first electrode 310 should be maximized. One way to achieve this is to have an at least partially overlapping region between the heat source 305 and the first junction 312. In an aspect, the first junction 312 may completely overlap the heat source 305, as illustrated in fig. 3A. This implies that the area of the first junction 312 should be at least as large as the area of the heat source 305 if a complete overlap is to occur.

Another way to enhance heat transfer is to increase the heat release area, which in turn will increase the heat dissipation capacity of the heat transfer device 300. For example, as illustrated in fig. 3B, the second junction 322 may have a larger area than the first junction 312. It is not a requirement that second junction 322 have a larger area, but with such a structure, the heat absorbed at first junction 312 can be released over a larger area at second junction 322.

In fig. 3B, both the first and

second junctions

312, 322 are illustrated as being on the same lateral surface of the TE layer 350, in this example an upper (first lateral) surface 352. However, this is not a requirement, as illustrated in fig. 4A and 4B, which illustrate a heat transfer device 400. Elements of heat transfer device 400 are numbered similarly to elements of heat transfer device 300, except that they begin with a "4" instead of a "3".

The structure of heat transfer device 400 (which is also active) may be similar to the structure of heat transfer device 300. For example, the thermal transfer device 400 may include a Thermoelectric (TE) layer 450, a first electrode 410, and a second electrode 420 (see fig. 4B). The first electrode 410 may be another example of a means for applying a first voltage, and the second electrode 420 may be another example of a means for applying a second voltage. A first electrode 410 (which may be formed of a metal) may interface with the TE layer 450 at a first junction 412, and a second electrode 420 (which may be formed of the same or different metal) may interface with the TE layer 450 at a second junction 422. The first junction 412 may begin at or near the left (first side) surface 456 and extend toward the right (second side) surface 458, and the second junction 422 may begin at or near the right (second side) surface 458 and extend toward the left (first side) surface 456. When there is a voltage difference between the first and

second electrodes

410, 420, it can be assumed that heat flows laterally within the TE layer 450 from the first electrode 410 to the second electrode 420. There may be partial or full overlap between the first junction 412 and the heat source 405. Further, the second junction 422 may have a larger area than the first junction 412.

However, unlike the thermal transfer device 300, the first and

second electrodes

410, 420 of the thermal transfer device 400 may be on opposing lateral surfaces. This implies that the first and

second junctions

412, 422 may also be part of the opposing lateral surfaces. In this example, the first and

second electrodes

410, 420 are illustrated as being on the upper surface 452 and the lower surface 454, respectively. That is, the first junction 412 may be part of the upper (first lateral) surface 452 and the second junction 422 may be part of the lower (second lateral) surface 454. Although not shown, it is of course possible to have a structure in which the first and

second electrodes

410, 420 are on the lower surface 454 and the upper surface 452, respectively.

Recall from above that the TE layers 350, 450 can be either P-type semiconductors or N-type semiconductors. It is also possible to have both P-type and N-type semiconductors in the heat transfer device, as illustrated in fig. 5A, 5B, and 5C. Fig. 5A illustrates a top view of heat-transfer device 500, fig. 5B illustrates one side view of heat-transfer device 500, and fig. 5C illustrates an opposite side view of heat-transfer device 500.

As illustrated, the heat transfer device 500 may include a first TE layer 550, a first electrode 510, and a second electrode 520. The first electrode 510 may be a further example of a means for applying a first voltage, and the second electrode 520 may be a further example of a means for applying a second voltage. From one perspective, the first TE layer 550, the first electrode 510, and the second electrode 520 may be considered similar to the TE layer 350, the first electrode 310, and the second electrode 320 of the heat transfer device 300. That is, the first TE layer 550 may be an N-type or P-type semiconductor and may have first and second lateral surfaces 552, 554 and first and second side surfaces 556, 558 (see fig. 5B). The first and

second electrodes

510, 520 may each be on a first or second

lateral surface

552, 554 of the first TE layer 550. For simplicity of description, it may be assumed that both the first and

second electrodes

510, 520 are on the first lateral surface 552, which implies that both the first and

second junctions

512, 522 are part of the first lateral surface 552. Both the first and

second electrodes

510, 520 may be formed of metal (the same or different). First knot 512 may begin or substantially begin at first side surface 556 and extend toward second side surface 558, and second knot 522 may begin or substantially begin at second side surface 558 and extend toward first side surface 556.

The heat transfer device 500 may further include a second TE layer 560, a third electrode 530, and a fourth electrode 540. The third electrode 530 may be an example of a means for applying a third voltage, and the fourth electrode 540 may be an example of a means for applying a fourth voltage. From one perspective, the second TE layer 560 and the third and

fourth electrodes

530, 540 can be considered mirror images of the first TE layer 550, the first electrode 510, and the second electrode 520 (see fig. 5A). For example, the second TE layer 560 may be a semiconductor of the opposite type to the first TE layer 550. The second TE layer 560 can have third and fourth lateral surfaces 562, 564 and third and fourth lateral surfaces 566, 568, with the third and fourth lateral surfaces 562, 564 being longer than the third and fourth lateral surfaces 566, 568 (see fig. 5C).

The corresponding surfaces of the first and second TE layers 550, 560 may define substantially parallel planes. That is, the planes of the third and fourth lateral surfaces 562, 564 may be substantially parallel to the planes of the first and second lateral surfaces 552, 554. Similarly, the plane of the third and fourth side surfaces 566, 568 may be substantially parallel to the plane of the first and second side surfaces 556, 558. Indeed, as illustrated in fig. 5A, the corresponding planes of the first and second TE layers 550, 560 may be substantially coplanar.

The third and

fourth electrodes

530, 540 may each be on a third or fourth

lateral surface

562, 564 of the second TE layer 560. Again for simplicity of description, it may be assumed that both the third and

fourth electrodes

530, 540 are on the third lateral surface 562, which implies that both the third and

fourth junctions

532, 542 are part of the third lateral surface 562. Both the third and

fourth electrodes

530, 540 may be formed of metal (the same or different).

As illustrated in fig. 5A, the first and second TE layers 550, 560 may be positioned side-by-side. Further, the third electrode 530 may be positioned adjacent to the second electrode 520, and the fourth electrode 540 may be positioned adjacent to the first electrode 510. This means that the third junction 532 (the interface between the third electrode 530 and the second TE layer 560) may begin at or substantially at the fourth side surface 568 and extend towards the third side surface 566. Further, the fourth junction 542 (at the interface between the fourth electrode 540 and the second TE layer 560) may begin or substantially begin at the third side surface 566 and extend toward the fourth side surface 568 (see fig. 5C).

The second and

third electrodes

520 and 530 may be coupled so as to be at the same potential. In this way, a series electrical path may be formed in order from the first electrode 510, the first TE layer 550, the second electrode 520, the third electrode 530, the second TE layer 560, and the fourth electrode 540. For example, assume that the voltage is applied such that the voltage at the first electrode 510 is higher than the voltage at the fourth electrode 540. A voltage drop will occur from the first electrode 510 to the second electrode 520 and another voltage drop will occur from the third electrode 530 to the fourth electrode 540. Subsequently in fig. 5A, the resulting current will flow in a left-to-right direction in the first TE layer 550 and in a right-to-left direction in the second TE layer 560. When the second and

third electrodes

520, 530 are electrically coupled, any voltage drop between them will be negligible. In one aspect, a single electrode may be used as the second and

third electrodes

520, 530.

This configuration may transfer heat in a parallel direction when the first and second TE layers 550, 560 are positioned side-by-side to form a series electrical path as illustrated in fig. 5A. For example, assume that voltages are applied to the first and

fourth electrodes

510, 540, as described immediately above. It is also assumed that the first TE layer 550 is a P-type semiconductor and the second TE layer 560 is an N-type semiconductor. In fig. 5A, heat will transfer laterally from left to right in both the first TE layer 550 and in the second TE layer 560. In the first TE layer 550, since the first TE layer 550 is P-type, heat will be transferred in the direction of current-from the first electrode 510 to the second electrode 520. In the second TE layer 560, since the second TE layer is N-type, heat will be transferred in the opposite direction of the current-from the fourth electrode 540 to the third electrode 530. In other words, the thermal path from the first electrode 510 to the second electrode 520 within the first TE layer 550 may be substantially parallel to the thermal path from the fourth electrode 540 to the third electrode 530 within the second TE layer 560.

It may be assumed that when there is a voltage difference between the first electrode 510 and the fourth electrode 540, heat flows laterally within the first TE layer 550 from the first electrode 510 to the second electrode 520, and also laterally within the second TE layer 560 from the fourth electrode 540 to the third electrode 530. That is, when power is applied between the first and

fourth electrodes

510, 540, heat may be absorbed at the first and

fourth junctions

512, 542 and released at the second and

third junctions

522, 532. If the first and second TE layers 550, 560 are P-type and N-type semiconductors, respectively, the potential applied to the first electrode 510 should be higher. If the first and second TE layers 550, 560 are N-type and P-type semiconductors, respectively, the potential applied to the fourth electrode 540 should be high.

In one aspect, the combined area of the first and

fourth junctions

512, 542 may at least partially overlap the heat source 505. The overlap may be complete to maximize heat absorption from the heat source 505. In another aspect, the combined area of the second and

third junctions

522, 532 may be larger than the combined area of the first and

fourth junctions

512, 542 to enhance heat release.

Although not shown, the second and

third junctions

522, 532 may be on a lateral surface opposite the first and

fourth junctions

512, 542. However, in one aspect, the second and

third junctions

522, 532 are portions of corresponding lateral surfaces. In other words, if the second electrode 520 is on the first lateral surface 552, the third electrode 530 may be on the third lateral surface 562. Conversely, if the second electrode 520 is on the second lateral surface 554, the third electrode 530 may be on the fourth lateral surface 564.

Furthermore, although not shown, one alternative is to electrically couple the first and

fourth electrodes

510, 540 instead of the second and

third electrodes

520, 530. In this alternative, assuming that the first and second TE layers 550, 560 remain as P-type and N-type semiconductors, respectively, a series electrical path may be formed in order from the third electrode 530, the second TE layer 560, the fourth electrode 540, the first electrode 510, the first TE layer 550, and the second electrode 520. In this alternative, if the voltage is applied such that the voltage at the third electrode 530 is higher than the voltage at the second electrode 520, a voltage drop from the third electrode 530 to the fourth electrode 540 will occur, and another voltage drop from the first electrode 510 to the second electrode 520 will occur. In other words, the voltage drop between the first and

second electrodes

510, 520 and between the third and

fourth electrodes

530, 540 will be in the same direction as the example device illustrated in fig. 5A, and thus the heat transfer direction will also be the same.

Any or all of the

heat transfer devices

300, 400, 500 and variations thereof may be incorporated into an apparatus, such as a mobile device. An example of such an apparatus is illustrated in fig. 6. The device 600 may include a chip 605 and a battery 635. Chip 605 is an example of a source of heat and battery 635 is an example of a source of power, the battery 635 configured to provide power to one or more components of device 600, including chip 605. Device 600 may also include a display 645, such as a Liquid Crystal Display (LCD), and a back cover 655 to house the internal components of device 600. In addition to chip 605 and battery 635, other internal components of device 600 may include a Printed Circuit Board (PCB)607, a Thermal Interface Material (TIM)603, and a support 625 (e.g., a Mg alloy support).

The apparatus 600 may incorporate a heat transfer device 615, which heat transfer device 615 may be any one of the

heat devices

300, 400, 500 or a variation thereof. In fig. 6, the rounded rectangles of the short dashed lines indicate portions of the heat transfer device 615 that can absorb heat from the chip 605, and the rounded rectangles of the long dashed lines indicate places where the heat can be released. The short dashed rounded rectangles may correspond to heat absorbing junctions (e.g.,

junctions

312, 412, 512, 542), and the long dashed rounded rectangles may correspond to heat releasing junctions (e.g.,

junctions

322, 422, 522, 532). By appropriate configuration of the heat transfer device 615, hot spots in the apparatus 600 may be mitigated.

For efficiency, electrodes that conduct heat from chip 605 may be positioned close to chip 605 where feasible. This is shown in fig. 7A, which fig. 7A illustrates a detailed example of a heat transfer device 615. For simplicity, some of the internal components of the device 600 (such as the PCB 607 and the bracket 625) are not shown. As illustrated, the first electrode 710 may be between the chip 605 and the TE layer 750. In other words, the first junction 712 may be a portion of a first lateral surface 752 of the TE layer 750 oriented toward the chip 605. The first electrode 710 may be yet another example of a means for applying a first voltage. First junction 712 may overlap chip 605. Further, the second junction 722 (which is between the second electrode 720 and the TE layer 750) may have a larger area than the first junction 712. The second electrode 720 may be yet another example of a means for applying the second voltage. The TE layer 750 may also have a second lateral surface 754, a first side surface 756, and a second side surface 758. The illustrated heat transfer device 615 may be similar to the vertically inverted variant of the heat transfer device 300 of fig. 3B.

In another aspect, fig. 7A and 7B may be considered to illustrate another detailed example of a heat-transferring device 615. For example, the particular heat transfer device 615 may include first and second TE layers 750, 760 having opposite semiconductor types, and also include first, second, third, and

fourth electrodes

710, 720, 730, and 740. The second TE layer 760 may have third and fourth lateral surfaces 762, 764 and third and fourth lateral surfaces 766, 768. From one perspective, this particular heat transfer device 615 may be viewed as a vertically inverted variant of the heat transfer device similar to fig. 5B and 5C. Referring back to fig. 7A and 7B, the first electrode 710 may be between the chip 605 and the first TE layer 750, and the fourth electrode 740 may also be between the chip 605 and the second TE layer 760. In other words, the first and

fourth junctions

712, 742 may be portions of the first and third

lateral surfaces

752, 762 of the first and second TE layers 750, 760 that are oriented toward the chip 605. The combination of the first and

fourth junctions

712, 742 may overlap the chip 605. Further, the second and

third junctions

722, 732 together may have a larger area than the first and

fourth junctions

712, 742 together.

In fig. 6, the heat transfer device 615 may be configured to transfer heat generated by the chip 605 to dissipate the heat to the cooling area of the mount 625. Fig. 8, 9, 10, and 11 illustrate other examples of

devices

800, 900, 1000, and 1100, which may include similar components to those of device 600, including chips (805, 905, 1005, 1105), TIMs (803, 903, 1003, 1103), PCBs (807, 907, 1007, 1107), shelves (825, 925, 1025, 1125), batteries (835, 935, 1035, 1135), displays (845, 945, 1045, 1145), and back covers (855, 955, 1055, 1155).

The

apparatus

800, 900, 1000, 1100 may incorporate a heat transfer device 815, 915, 1015, 1115. In fig. 8, a heat transfer device 815 may be configured to transfer heat generated by the chip 805 to dissipate the heat to a cooling area of the rack 825. Note that heat transfer device 815 is between chip 805 and mount 825, while in fig. 6 mount 625 is between chip 605 and heat transfer device 615. In fig. 9, the heat transfer device 915 may be configured to dissipate heat to the battery 935. In fig. 10, the heat transfer device 1015 may be configured to dissipate heat to a cooling region of the display 1045. In fig. 11, the heat transfer device 1115 may be configured to dissipate heat to a cooling region of the back cover 1155.

The heat-transfer devices 815, 915, 1015, 1115 illustrated in fig. 6, 8, 9, 10, and 11 may be any of the heat-

transfer devices

300, 400, 500, 615 illustrated in fig. 3A, 3B, 4A, 4B, 5A, 5B, 5C, 6, 7A, and 7B, and variations thereof. Additionally, although specific reference may have been made to a mobile device, the scope of the disclosure is not limited in this respect. The various aspects may be applicable in many systems where active heat transfer capability is desired.

Fig. 12A-12C illustrate views of various stages of an example method of forming a heat-transfer device, such as heat-transfer device 300. Fig. 12A illustrates a stage in which a passivation layer 1227 may be formed on a shelf 1225 (such as a Mg alloy shelf). For example, SiNx or SiOx may be deposited and patterned to form a passivation layer 1227 on the support 1225. The passivation layer 1227 may provide electrical insulation.

Fig. 12B illustrates a stage in which a TE layer 1250 (a P-type or N-type semiconductor) may be formed on the passivation layer 1227. For example, a thin film semiconductor may be applied and patterned to form the TE layer 1250.

Fig. 12C illustrates a stage in which first and

second electrodes

1210, 1220 may be formed on the TE layer 1250. For example, one or more metals may be deposited and patterned to form the first and

second electrodes

1210, 1220.

It is noted that the stages illustrated in fig. 12A may not be strictly necessary. It is to be appreciated that to form the TE layer 1250, it is desirable to have a support structure, such as a passivation layer 1227, upon which the semiconductor material is deposited. Different types of support structures may then be utilized depending on considerations such as the desired thermal mitigation application, cost, ease of manufacture, and the like.

Fig. 13 illustrates a flow diagram of an example method 1300 for forming a heat transfer device, such as heat transfer device 300. In block 1310 of method 1300, a passivation layer 1227 may be formed (see, e.g., fig. 12A). In block 1320, a TE layer 1250 may be formed (see, e.g., fig. 12B). In block 1330, first and

second electrodes

1210, 1220 may be formed on the TE layer 1250 (e.g., see fig. 12C). The resulting heat transfer device of method 1300 may include some or all of the features of heat transfer device 300 described in detail above, and thus will not be repeated. It should be kept in mind that it is relatively straightforward to alter the method 1300 to achieve some or all of the aspects of the heat transfer apparatus and its undescribed variations described in detail above.

Fig. 14A-14C illustrate stages of another method for forming a heat-transfer device, such as heat-transfer device 500. Fig. 14A illustrates a stage in which a passivation layer 1427 may be formed on a support 1425, such as a Mg alloy support. This is similar to the stage illustrated in fig. 12A, so details will not be repeated. Further, like fig. 12A, this stage of fig. 14A is not necessary.

Fig. 14B illustrates a stage in which first and second TE layers 1450, 1460 (one for each semiconductor type) may be formed over passivation layer 1427. For example, a thin film semiconductor of one type (e.g., P-type) may be applied and patterned to form a first TE layer 1450, and a thin film semiconductor of the opposite type (e.g., N-type) may be applied and patterned to form a second TE layer 1460.

Fig. 14C illustrates a stage in which first and

second electrodes

1410, 1420 may be formed on a first TE layer 1450, and in which third and

fourth electrodes

1430, 1440 may be formed on a second TE layer 1460. For example, one or more metals may be deposited and patterned to form the first, second, third, and

fourth electrodes

1410, 1420, 1430, and 1440. The second and

third electrodes

1420, 1430 may be formed to be electrically coupled to each other. It is noted that, in an aspect, a single electrode may be formed to serve as the second and

third electrodes

1420, 1430. Although not shown, in the alternative, the first and

fourth electrodes

1410, 1440 may be formed to be electrically coupled to each other. In alternative aspects, a single electrode can be formed to serve as the first and

fourth electrodes

1410, 1440.

Fig. 15 illustrates a flow diagram of another example method 1500 for forming a heat-transfer device, such as heat-transfer device 500. In block 1510 of method 1500, a passivation layer 1427 may be formed (see, e.g., fig. 14A). In block 1520, a first TE layer 1450 may be formed, and in block 1525, a second TE layer 1460 may be formed (see, e.g., fig. 14B). In block 1530, first and

second electrodes

1410, 1420 may be formed on the first TE layer 1450, and in block 1535, third and

fourth electrodes

1430, 1440 may be formed on the second TE layer 1460 (see, e.g., fig. 14C).

The resulting heat transfer device of method 1500 may include some or all of the features of heat transfer device 500 described in detail above, and thus will not be repeated. And again it should be kept in mind that it is relatively straightforward to alter the method 1500 to arrive at some or all of the examples of the heat transfer apparatus and its non-illustrated variations described in detail above.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Furthermore, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the examples disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosed subject matter.

The methods, sequences and/or algorithms described in connection with the examples disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.

Accordingly, one aspect may include a computer readable medium embodying a method for forming an active heat transfer device. Thus, the scope of the disclosed subject matter is not limited to the illustrated examples and any means for performing the functionality described herein are included.

While the foregoing disclosure shows illustrative examples, it should be noted that various changes and modifications could be made herein without departing from the scope of the disclosed subject matter as defined by the appended claims. The functions, steps and/or actions of the method claims in accordance with the examples described herein need not be performed in any particular order. Furthermore, although elements of the examples may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.

Claims

1. A heat transfer device comprising:

a Thermoelectric (TE) layer having a first lateral surface, a second lateral surface, a first side surface, and a second side surface, wherein each of the first and second lateral surfaces is longer than each of the first and second side surfaces;

a first electrode on the first lateral surface of the TE layer, the first electrode configured to interface with the TE layer at a first junction; and

a second electrode on the first lateral surface or the second lateral surface of the TE layer, the second electrode configured to interface with the TE layer at a second junction,

wherein the heat transfer device is configured to: transferring heat generated by a heat source laterally within the TE layer from the first electrode to the second electrode when a voltage difference is applied between the first electrode and the second electrode, an

Wherein the first electrode is configured to: thermally conducting heat from the heat source to the TE layer at the first junction, and

wherein the first junction overlaps the heat source such that the first electrode is between the heat source and the TE layer.

2. The heat transfer device of claim 1,

wherein the first junction is a contact region between the first electrode and the TE layer and the second junction is a contact region between the second electrode and the TE layer, and

wherein the second junction has a larger area than the first junction.

3. The heat transfer device of claim 1,

wherein the first junction starts at or substantially starts at the first side surface and extends towards the second side surface, an

Wherein the second junction begins at or substantially begins at the second side surface and extends toward the first side surface.

4. The heat transfer device of claim 1, wherein the TE layer is a first TE layer, the heat transfer device further comprising:

a second TE layer having a third lateral surface, a fourth lateral surface, a third side surface, and a fourth side surface, wherein each of the third and fourth lateral surfaces is longer than each of the third and fourth side surfaces;

a third electrode on the third lateral surface or the fourth lateral surface of the second TE layer, the third electrode configured to interface with the second TE layer at a third junction,

a fourth electrode on the third lateral surface of the second TE layer, the fourth electrode configured to interface with the second TE layer at a fourth junction,

wherein the plane of the first lateral surface is substantially parallel to the plane of the third lateral surface, the plane of the second lateral surface is substantially parallel to the plane of the fourth lateral surface, the plane of the first side surface is substantially parallel to the plane of the third side surface, and the plane of the second side surface is substantially parallel to the plane of the fourth side surface,

wherein the second electrode and the third electrode are electrically coupled such that a series electrical path is formed in order from the first electrode, the first TE layer, the second electrode, the third electrode, the second TE layer, and the fourth electrode,

wherein the heat transfer device is configured to: transferring heat generated by the heat source laterally within the first TE layer from the first electrode to the second electrode and within the second TE layer from the fourth electrode to the third electrode when a voltage difference is applied between the first electrode and the fourth electrode, an

Wherein the first electrode is configured to: thermally conducting heat from the heat source to the first TE layer at the first junction, and the fourth electrode is configured to: thermally conducting heat from the heat source to the second TE layer at the fourth junction.

5. The heat transfer device of claim 4, wherein the first TE layer and the second TE layer are positioned side-by-side such that a thermal path from the first electrode to the second electrode within the first TE layer is substantially parallel to a thermal path from the fourth electrode to the third electrode within the second TE layer.

6. The heat transfer device of claim 4, wherein the first and third lateral surfaces are substantially coplanar and/or the second and fourth lateral surfaces are substantially coplanar and/or the first and third side surfaces are substantially coplanar and/or the second and fourth side surfaces are substantially coplanar.

7. The heat transfer device of claim 4, wherein the combination of the first junction and the fourth junction overlap the heat source such that the first electrode is vertically between the heat source and the first TE layer and the second electrode is vertically between the heat source and the second TE layer.

8. The heat transfer device of claim 4,

wherein the first junction is a contact area between the first electrode and the TE layer, the second junction is a contact area between the second electrode and the TE layer, the third junction is a contact area between the third electrode and the second TE layer, and the fourth junction is a contact area between the fourth electrode and the second TE layer, and

wherein a combination of the second junction and the third junction has a larger area than a combination of the first junction and the fourth junction.

9. The heat transfer device of claim 4, wherein the second and third electrodes are on the first and third lateral surfaces, respectively, or on the second and fourth lateral surfaces, respectively.

10. The heat transfer device of claim 4,

wherein the first junction starts at or substantially starts at the first side surface and extends towards the second side surface,

wherein the second junction begins at or substantially begins at the second side surface and extends toward the first side surface,

wherein the third junction begins at or substantially begins at the fourth side surface and extends toward the third side surface, an

Wherein the fourth junction begins or substantially begins at the third side surface and extends toward the fourth side surface.

11. The heat transfer device of claim 4, wherein a single electrode functions as the second electrode and as the third electrode.

12. An electronic device, comprising:

a chip;

a battery configured to provide power to the chip; and

a heat transfer device configured to actively transfer heat away from the chip, the heat transfer device comprising:

wherein the first junction overlaps the chip,

wherein the heat transfer device is configured to: transferring heat generated by the chip within the TE layer laterally from the first electrode to the second electrode when the cell applies a voltage difference between the first electrode and the second electrode,

wherein the first electrode is configured to: thermally conducting heat from the chip to the TE layer at the first junction, and

13. The apparatus as set forth in claim 12,

wherein the second junction has a larger area than the first junction.

14. The apparatus as set forth in claim 12,

15. The apparatus of claim 12, wherein the first electrode is vertically between the chip and the TE layer.

16. The apparatus as set forth in claim 12,

wherein the TE layer is a first TE layer and the heat transfer device further comprises:

a third electrode on the third lateral surface or the fourth lateral surface of the second TE layer, the third electrode configured to interface with the second TE layer at a third junction; and

wherein the first TE layer and the second TE layer are positioned side-by-side such that a thermal path from the first electrode to the second electrode within the first TE layer is substantially parallel to a thermal path from the fourth electrode to the third electrode within the second TE layer,

wherein a combination of the first junction and the fourth junction overlaps the chip,

wherein the heat transfer device is configured to: when the cell applies a voltage difference between the first electrode and the fourth electrode, heat generated by the chip is transferred laterally within the first TE layer from the first electrode to the second electrode and within the second TE layer from the fourth electrode to the third electrode, an

Wherein the first electrode is configured to: thermally conducting heat from the chip to the first TE layer at the first junction, and the fourth electrode is configured to: thermally conducting heat from a heat source to the second TE layer at the fourth junction.

17. The apparatus as set forth in claim 16,

18. The apparatus as set forth in claim 16,

19. The apparatus of claim 16, wherein the first electrode is vertically between the chip and the first TE layer and the fourth electrode is vertically between the chip and the second TE layer.

20. The apparatus of claim 12, further comprising:

a display;

a rear cover; and

a stand between the display and the back cover,

wherein the heat transfer device is configured to: transferring heat generated by the chip so as to dissipate the heat to any one or more of a cooling region of the bracket, the battery, a cooling region of the display, and a cooling region of the back cover.

21. A method of forming a heat transfer device, comprising:

forming a Thermoelectric (TE) layer having a first lateral surface, a second lateral surface, a first side surface, and a second side surface such that each of the first lateral surface and the second lateral surface is longer than each of the first side surface and the second side surface;

forming a first electrode on the first lateral surface of the TE layer such that the first electrode interfaces with the TE layer at a first junction; and

forming a second electrode on the first lateral surface or the second lateral surface of the TE layer such that the second electrode interfaces with the TE layer at a second junction,

wherein the heat transfer device is formed such that heat generated by a heat source is transferred laterally within the TE layer from the first electrode to the second electrode when a voltage difference is applied between the first electrode and the second electrode,

wherein the heat transfer device is formed such that the first electrode thermally conducts heat from the heat source to the TE layer at the first junction, and

wherein the first electrode is formed such that the first junction overlaps the heat source such that the first electrode is located between the heat source and the TE layer.

22. The method of forming the heat transfer device of claim 21,

wherein the first electrode is formed to be vertically located between the heat source and the TE layer,

wherein the second electrode is formed such that the second junction has a larger area than the first junction.

23. The method of forming the heat transfer device of claim 21,

wherein the first electrode is formed such that the first junction starts at or substantially starts at the first side surface and extends towards the second side surface, an

Wherein the second electrode is formed such that the second junction starts at or substantially starts at the second side surface and extends towards the first side surface.

24. The method of forming the heat transfer device of claim 21, wherein forming the TE layer comprises forming a first TE layer, the method further comprising:

forming a second TE layer having a third lateral surface, a fourth lateral surface, a third side surface, and a fourth side surface such that each of the third and fourth lateral surfaces is longer than each of the third and fourth side surfaces;

forming a third electrode on the third lateral surface or the fourth lateral surface of the second TE layer such that the third electrode interfaces with the second TE layer at a third junction; and

forming a fourth electrode on the third lateral surface of the second TE layer such that the fourth electrode interfaces with the second TE layer at a fourth junction,

wherein the first TE layer and the second TE layer are formed such that a plane of the first lateral surface is substantially parallel to a plane of the third lateral surface, a plane of the second lateral surface is substantially parallel to a plane of the fourth lateral surface, a plane of the first side surface is substantially parallel to a plane of the third side surface, and a plane of the second side surface is substantially parallel to a plane of the fourth side surface,

wherein the second electrode and the third electrode are formed to be electrically coupled to each other such that a series electrical path is formed in order from the first electrode, the first TE layer, the second electrode, the third electrode, the second TE layer, and the fourth electrode,

wherein the heat transfer device is formed such that when a voltage difference is applied between the first and fourth electrodes, heat generated by the heat source is transferred laterally within the first TE layer from the first electrode to the second electrode and within the second TE layer from the fourth electrode to the third electrode, an

Wherein the heat transfer device is formed such that the first electrode thermally conducts heat from the heat source to the first TE layer at the first junction and the fourth electrode thermally conducts heat from the heat source to the second TE layer at the fourth junction.

25. The method of forming the heat transfer device of claim 24,

wherein the first electrode and the fourth electrode are respectively formed to be vertically located between the heat source and the first TE layer and the second TE layer,

wherein the second electrode and the third electrode are formed such that a combination of the second junction and the third junction has a larger area than a combination of the first junction and the fourth junction.

26. The method of forming the heat transfer device of claim 24 wherein the first TE layer and the second TE layer are formed such that the first lateral surface and the third lateral surface are substantially coplanar, the second lateral surface and the fourth lateral surface are substantially coplanar, the first side surface and the third side surface are substantially coplanar, and the second side surface and the fourth side surface are substantially coplanar.

27. The method of forming the heat transfer device of claim 24,

wherein the first electrode is formed such that the first junction starts at or substantially starts at the first side surface and extends towards the second side surface,

wherein the second electrode is formed such that the second junction starts at or substantially starts at the second side surface and extends towards the first side surface,

wherein the third electrode is formed such that the third junction starts at or substantially starts at the fourth side surface and extends toward the third side surface, an

Wherein the fourth electrode is formed such that the fourth junction starts at or substantially starts at the third side surface and extends toward the fourth side surface.

28. A heat transfer device comprising:

means for applying a first voltage on the first lateral surface of the TE layer, the means for applying a first voltage interfacing with the TE layer at a first junction; and

means for applying a second voltage on the first lateral surface or the second lateral surface of the TE layer, the means for applying a second voltage interfacing with the TE layer at a second junction,

wherein the heat transfer device is configured to: transferring heat generated by a heat source within the TE layer laterally from the means for applying a first voltage to the means for applying a second voltage when a voltage difference is applied between the means for applying a first voltage and the means for applying a second voltage,

wherein the means for applying a first voltage thermally conducts heat from the heat source to the TE layer at the first junction, and

wherein the first junction overlaps the heat source such that the means for applying a first voltage is between the heat source and the TE layer.

29. The heat transfer device of claim 28, wherein the TE layer is a first TE layer, the heat transfer device further comprising:

means for applying a third voltage on the third lateral surface or the fourth lateral surface of the second TE layer, the means for applying a third voltage interfacing with the second TE layer at a third junction; and

means for applying a fourth voltage on the third lateral surface of the second TE layer, the means for applying a fourth voltage interfacing with the second TE layer at a fourth junction,

wherein the means for applying a third voltage and the means for applying a second voltage are electrically coupled such that a series electrical path is formed in order from the means for applying a first voltage, the first TE layer, the means for applying a second voltage, the means for applying a third voltage, the second TE layer, and the means for applying a fourth voltage,

wherein the heat transfer device is configured to: when a voltage difference is applied between the means for applying a first voltage and the means for applying a fourth voltage, heat generated by a heat source is transferred laterally within the first TE layer from the means for applying a first voltage to the means for applying a second voltage and laterally within the second TE layer from the means for applying a fourth voltage to the means for applying a third voltage, and

wherein the means for applying a first voltage thermally conducts heat from the heat source to the first TE layer at the first junction and the means for applying a fourth voltage thermally conducts heat from the heat source to the second TE layer at the fourth junction.